[Xen-devel] Re: [PATCH][1/4] Enable 1GB for Xen HVM host page

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 24/02/2010 04:25, "Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx> wrote:

> When allocating guest memory without the patch, Xend will treat 3G-4G
> as normal memory, ignoring the 3.75-4G MMIO hole. This patch modifies
> MMIO start address to be 1GB aligned and could fix the issue.
> 
> Indeed, this patch may have some influence to pure 32bit guest,
> changing its max memory from 3.75G to 3G.
> 
> Anyway, we can change it to alloc 2M pages between 3G and 4G if you
> think this particular patch is improper.

I would expect it to fall back to 2MB extents, and from there back to 4kB
extents as necessary, for any range where: (a) the range to be allocated for
is not 1GB-sized and -aligned; or (b) no 1GB extents are available from
Xen's free pool.

 -- Keir



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